This invention relates to the hydrometallurgical treatment process for extracting platinum group metals from a flotation concentrate.
Conventionally, platinum group metals are extracted from a flotation concentrate in a matte smelting and converting process followed by further refining for the extraction of the platinum group metals.
According to the invention there is provided a hydrometallurgical treatment process for extracting platinum group metals from a flotation concentrate comprising the steps of:
leaching of the flotation concentrate to dissolve base metal sulphides in the flotation concentrate so as to form a filtrate and a residue;
separation of the filtrate from the residue;
roasting the residue to form a calcine; and
chlorination of the calcine to dissolve the platinum group metals into solution.
Typically, the process includes the additional steps of:
adsorption of the platinum group metals onto an ion exchange resin; and
recovery of the platinum group metals from the ion exchange resin.
Preferably, the roasting step involves oxidation or reduction, more preferably oxidation at up to 1000xc2x0 C.
Typically, the method includes the step of recovering Osmium from the off-gas from the roasting step.
The chlorination step preferably comprises countercurrent chlorination of the calcine at approximately 80xc2x0 C. and 3.5N HCl.
The separation step typically comprises filtration followed by the additional steps of neutralisation of the filtrate; precipitation of base metal sulphides and flotation of precipitated sulphides into a concentrate.
The step involving adsorption of the platinum group metals onto an ion exchange resin may be followed by:
desorption of the platinum group metals from the resin with thiourea at approximately 80xc2x0 C. followed by water washing of the stripped resin; and/or
precipitation of the platinum group metals from the eluate with caustic solution.
Various embodiments of the invention are described in detail in the following passages of the specification which refer to the accompanying drawings. The drawings, however, are merely illustrative of how the invention might be put into effect, so that the specific form and arrangement of the features shown is not to be understood as limiting on the invention.